The present invention relates to control arrangements for photographic apparatus and in particular for motion picture cameras. In these cameras a bridge circuit is present which comprises at least one light-sensitive element. Further, a differential amplifier has its two inputs connected to the bridge circuit output and has an output connected to an electromagnetic adjustment means which controls the opening in the diaphragm in such a manner as to balance the bridge circuit. In order to accomplish this, the differential amplifier is followed by a first and second threshold circuit. The electromagnetic adjustment means adjusting the diaphragm opening are energized to operate in a first direction when the first threshold circuit does not furnish an output signal and in a second direction when the second threshold circuit does furnish an output signal.